Hi Brian,
I would like to tell you that your question has been answered in the GCC
documentation for inline assembly.
Your first question related to operand numbering,
Operands corresponding to the C expressions are represented by %0, %1 ...
etc.
In the assembler template, each operand is referenced by numbers.
Numbering is done as follows. If there are a total of n operands (both input
and output inclusive),
then the first output operand is numbered 0, continuing in increasing order,
and the last input operand is numbered n-1.
Now getting back to your question, a single variable may serve as both the
input
and the output operand.
Such cases may be specified in "asm" by using matching constraints.
asm ("incl %0" :"=a"(var):"0"(var));
For more information on the same kindly refer
http://www.ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html
Regards
Manjunath S M
Brian O'Mahoney-4 wrote:
>
> A very simple question, but no-where explicitly documented, when using
> extended assembly, how are operand numbers ie %n relate to input and
> output
> constraint-lists ?
>
> Do they independently count from zero, in each constraint list? What if an
> operand is in & out put?
>
> Thanks, Brian
>
> --
> Greetings (mit freundlichen Grüßen), Brian.
>
> Dr. Brian O'Mahoney Email: omb@xxxxxxxxxxx
>
>
--
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